Evacuation Action of Medaka under Increased Rate of Flow

Abstract

The relationship between the rate of flow and natant action for medaka, a kind of cyprinodont that is designated as an endangered species, was investigated, revealing that the fish evacuates into areas with a gentle flow, such as behind waterweed when the rate of flow increases. The majority of a school begins evacuation when the rate is between 18 and 22 cm/s (about 6 to 7 times the total length of a medaka). It was found that the rate of flow at which medaka move safely is below 15 to 20 cm/s.